1. Field of the Invention
The present invention relates to an aquascooter which is designed to be used by a scubadiver in scubadiving and other underwater activities, and more particularly to an aquascooter which is guaranteed free of destruction by explosion of hydrogen which is produced from chemical reaction in battery or by electrolysis of seawater leaking into the scooter housing.
2. Description of the Prior Art
As is well known, aquascooters have been widely used by scubadivers in scubadiving and other underwater athletic activities. A conventional aquascooter generally comprises, in a housing with carrying handles, a battery, a driving motor and a power transmission to transmit driving power to a propeller, which appears out of the housing.
The housing of the conventional aquascooter has no partitions to define separate compartments each allotted to the battery, the driving motor and the power transmission. These different parts are together put in a single housing space. The battery is fixed to the housing.
The conventional aquascooter has no safety means to prevent hydrogen explosion. Hydrogen gas is produced from chemical reaction in the battery or by electrolysis by the battery of seawater leaking into the scooter housing. Hydrogen explosion is caused by spark for instance, appearing in the brush of the driving motor.
The conventional aquascooter has no means to absorb seawater leaking into the housing. Its housing ha only two carrying handles at opposite sides. A propeller shroud enclosing the propeller is of circular shape.
Such conventional aquascooters have been popular among scubadivers in scubadiving and other underwater activities for a long time. Scubadivers have been increasing, and their underwater activities with the aid of aquascooters must be guaranteed free of any danger. As mentioned above, the conventional aquascooter has no safety means to prevent hydrogen explosion, which is caused by exposing hydrogen gas to spark for instance, appearing in the brush of the driving motor. Such hydrogen gas is produced from chemical reaction in the battery or by electrolysis by the battery of seawater leaking into the scooter housing. Hydrogen explosion will break mechanical parts and aquascooter body, and there is a fear of injuring scubadivers. In fact, many accidents have been reported.
Leak of seawater into the housing will cause corrosion and damage of parts, reducing the endurance and safety of the aquascooter. The conventional aquascooter has no remedy for this problem.
Two handles of the aquascooter body may be convenient for carrying it by two persons on land. They stand on the opposite sides of the aquascooter, each of them to be held by one hand. However it is inconvenient for a single person to carry in his arms with both hands gripping the handles.
The round propeller shroud makes it difficult for a scubadiver to hold his body parallel to the aquascooter body in water.
Among these defects, the problem of hydrogen explosion is of greatest concern. Therefore, this must be discussed first.
Thermal reaction in hydrogen explosion is theoretically expressed by: EQU H.sub.2 +1/2 O.sub.2 =H.sub.2 O+68.3 K cal
When a mixture of hydrogen and air or oxygen is ignited, a chain of above reactions will be triggered, generating a large amount of heat instantaneously to cause steam to expand exlosively. This is called the hydrogen explosion. The chemical reaction is most vigorous when the hydrogen-to-air ratio is 2 to 5 in volume (approximately 29% in volume). The flammable range is from 4.1 to 74.2% in volume.
Now, the development of chemical reaction to explosion in an aquascooter is described below. First, the development of chemical reaction to explosion of hydrogen gas from a battery is described. ##STR1##
In the normal charging and discharging process in the battery, no hydrogen gas can be produced according to the theory. A small amount of hydrogen gas, in fact, appears when charging is completed, or when the battery is overcharged. When repeatedly used, a battery is apt to produce hydrogen gas. It has been found that if a battery is put in a closed space, hydrogen gas is produced and released from the battery until the atmosphere in the closed space reaches the explosion limit. The amount of hydrogen gas produced depends on the temperature of the battery and surrounding atmosphere. Specifically, no hydrogen gas is produced at 40 degrees C.; 7 to 15 cc/H at 60 degrees C,; 20 to 120 cc/H at 70 degrees C.; and 120 to 250 cc/H at 80 degrees C. Hydrogen yield increases as the temperature rises. The explosion limit will be reached in 10 to 20 hours at 60 degrees C; in 1.2 to 7.5 hours at 70 degrees C.; and in 0.6 to 1.2 hours at 80 degrees C. Explosion is caused when such flammable atmosphere is ignited by spark appearing in the brushes of an electric motor, in the contacts of relays and switches, or by flame appearing in wires and connectors when heated by heavy current flowing in these wires and connectors.
In the conventional aquascooter a battery is fixed in the housing, and therefore, the battery cannot be removed and will be repeatedly charged in situs of the closed space, thus accumulating hydrogen gas to the explosion limit in the housing. The battery, driving motor, clutch and wirings are contained together in the same housing space, and therefore if the temperature of the battery rises, the flammable hydrogen-to-air ratio being reached in a relatively short time at an increased temperature will be a great danger of hydrogen explosion, which may triggered by spark appearing in the electric system in the same housing space.
Another possibility of hydrogen explosion is found in hydrogen electrolysis by the battery of seawater, which leaks into the aquascooter housing.
In electrolysis of seawater, salt and other ingredients are chemically bound with hydroxyl ions to produce a large amount of hydrogen and chlorine gas. This chemical reaction is caused when the positive and negative terminals of the battery are submerged in seawater. When the flammable hydrogen-to-air ratio has been reached, and when spark appears in the flammable atmosphere, a hydrogen explosion will be caused. In fact, there were may explosions due to electrolysis of seawater because conventional aquascooters have no means to prevent leakage of seawater into the housing.